Apparatus and process for the removal of insulation from wire

ABSTRACT

The apparatus and process for the rapid and effective removal of organic insulating material such as Teflon (Trademark of E. I. du Pont de Nemours &amp; Co.) TFE, polytetrafluoroethylene, FEP, fluorinated ethylene-propylene, or the like, from fine or superfine wire by the controlled application of a stream of hot gas. The apparatus includes testing equipment to verify the proper operation of the insulation stripping apparatus.

United States Paten Angelo et al. [451 Jan. 18, 1972 [541 APPARATUS AND PROCESS FOR THE [56] References Cited VAL OF INSULATION FROM UNITED STATES PATENTS 3,351,329 ll/1967 Thomas ..34/155 X 72] Inventors: Raymond W. Angelo, EIIICIWCH; Howard G. 3 3 7 04 2 19 3 Troope et 3|. 3 5 x Hwahhlen, Johnson City, both of 3,402,447 9/1968 Mettler ..263/3 x I t tlo al B i M hi C [73] Asslgnee l f g g f ac nes orpma Primary Examiner-John .I. Camby Attorney-Hanifin and Jancin and Charles S. Neave [22] Filed: May 7, 1970 [211 App]. No.: 35,359 [57] ABSTRACT The apparatus and process for the rapid and effective removal of organic insulating material such as Teflon (Trademark of E. il l. du Pom de Nemouts & T polyeuafluoroethylene' [58] Fieid 34/155 FEP, fluorinated ethylene-propylene, or the like, from fine or GAS FLOW REGULATOR superfine wire by the controlled application of a stream of hot gas. The apparatus includes testing equipment to verify the proper operation of the insulation stripping apparatus.

8 Claims, 1 Drawing Figure Pmmmmsmz 3.635.454

RAYMOND W. ANGELO HOWARD G. HOUGHTALEN BACKGROUND OF THE INVENTION l-IField of the Invention This invention relates to the apparatus and: process for removal of insulationmaterial from wire, and more particularly, to the removal of organic materials such as polytetrafluorethylene or fluorinated ethylene-propylene films which function as insulating covers for fine or superfine electrically conductive wire sometimes identified as microfine wire. 1

2. Description of the PriorArt in the past it has been common practice to individually strip the insulation from the ends of large-size wires by the use of hand tools. In many instances, the procedure has been automated through the use of program-controlled machine operations. 1

-Various processes have been employed to effect the removal of organic film insulation from the surface of wire conductors to enable electrically conducting anchorage for such wires to terminals. Wires of relatively large diameter, i.e., larger than 0.020 inch in diameter may be satisfactorily stripped of insulation mechanically by such methodsas wire brushingor brushing with a glass fiber mat. However, such methods are inadequate or unsatisfactory for the removal of wire insulation from the surface of wires 0.020 inchin diameter or smaller, because such small diameter conductors are easily and frequently damaged by the use of mechanical abrading. U.S. Pat. No. 1,835,801 discloses apparatus to complete animperfect stripping of the ends of wires by a supplemental operation involving the burning of the remnant insulation in a gas flame. In U.S. Pat. No. 2,73l,372 discloses apparatus to complete an imperfect stripping of the ends of wires by a supplemental operation involving the burning of the remnant insulation in a gas flame. ln U.S. Pat. No. 2,713,372 apparatus is disclosed which includes a provision for removing theinsulation from the ends of wire by charting the insulation through the-application of an acetylene flame. The charred insulation is then removed and the wire cleaned by the abrading action of a wire brush.

U.S. "Pat. No. 3,331,718 shows methods of removing selected areas of resinous insulating films by contacting the selected areas of insulating film with-a chemical reagent which will remove or dissolve the film.

SUMMARY OF THE INVENTION The apparatus and process of the instant invention provides a means for. removing the insulation from superfine or microwire with diameters of less than 20 mils. The apparatus is particularly adapted to accommodate wire coatings with the newer Teflon-type insulation materials made of TFE or FEP polymers.

Briefly, the apparatus comprises a supply of nitrogen gas, a device to regulate the flow of the gas, controllable gas-heating means, a quartz tube having a small orifice therein for directing the flow of heated gas, and means to feed insulated microwire past the orifice in the quartz tube.

Additionally, the apparatus includes a circuit and test apparatus for testing the area of insulation removal to determine if the insulation has been satisfactorily removed from the selected portion of the microwire.

It is the primary object of the invention to provide an efficient and reliable apparatus and method for removing insulation from microwire.

The foregoing and other objects, features and advantages of the invention will be apparent from the following, more par ticular description of a preferred embodiment of the invention, as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a diagrammatic showing of the insulation removal apparatus for fine or microwire according to the present invention.

2 DESCRIPTION OF THE PREFERRED EMBODIMENT A type of commercially available polymer material identifiedas Teflon TFE, or polytetrafluorethylene has been come into use as wire-insulating coating. A newer polymertype material identified as Teflon F5? or fluorinated ethylenepropylene is also now used to coat electrical wires. As a wirecoating, the Teflon FEP polymer can be applied 'by extrusion techniques around the electrical conductor. Consequently, the Teflon FEP will possess the extended molecular chains of the high-temperature extrusion process held in place by normal temperature. At high temperature, these stresses are relieved and the coating shrinks by an elastic memory. With the Teflon-TFE-type polymer, a'different situation occurs. The Teflon TFE must be applied by a dispersion process which does not leave the stresses of plastic memory. Consequently, it cannot be removed from microwires by the application of temperatures near the extrusion temperature.

Because of its inertness and dielectric properties, Teflon is a particularly desirable insulation material. However, while its chemical inertness is desirable in use, it does eliminate the stripping function by chemical process. Further, Teflon is thermally one of the more resistant polymers. Experimentation has provided indication that the material does degrade almost completely at temperatures of approximately 500 C.

The drawing is a diagrammatic showing of the insulation removal apparatus comprising a supply of nitrogen gas 10 that is coupled to a filtering means 11. The gas output from the filter 11 is coupled through a flow regulator 12 which functions to control the rate of nitrogen gas. The gas flow from the regulator 12 passes througha serpentine heater that includes a tungsten-type heating element'l4. A variac 15 functions to regulate the voltage applied to the heating element 14. The serpentine'heater 13 includes a quartz tube which narrows down to a small diameter orifice at its lowermost portion.

The insulated microwire is positioned beneath the orifice in the quartz tube by threading through opposing glass or metal tubes 17. The wire. 16 is fed from the feed spool 18 to the takeup spool 19. Lateral motion of the wire 16 is controlled by means of pressure pads 20 positioned between the tubes 17 and the feed spool 18, also between the tubes 17 and the takeup spool 19.

Electrical contacts are positioned immediately before the takeup spool 19 as a part of an electrically conductive path testing circuit which includes the buzzer 22 and the battery 23. The test circuit is arranged so that the contacts 21 will activate the buzzer 22 if the circuit is completed via the portion of wire 16 which has the insulative coating removed from a predetermined portion.

The diagram shows a sliding platform 24 which slides as a mount for the wire support and spool apparatus. In the preferred method of operation, the wire is moved under the stream of hot nitrogen gas emitted from the orifice in the quartz tube portion of the serpentine heater 13. The temperature of the nitrogen gas stream is a function of the voltage at various controlled flow settings. The effectiveness of the stripping operation is also a function of the distance between the wire 16 and the orifice opening in the quartz tube portion of the serpentine heater l3. Empirically, it has been determined that for Teflon FEP, suitable stripping operations can be obtained when the temperature is in the range of 800 and 900 C. with this type of temperature control, a complete depolymerization of the polymer insulating coating can be achieved.

In accordance with the present invention, suitable and effective stripping operations can be controlled by the proper selection of parameters. The system is devoid of knife edges to wear out, and damage the electrical conductor during the insulation stripping operation.

Also, variation in diameter of the microwire and in the thickness of the insulation, or in the concentricity of the insulation around the conductor, does not cause difficulty in achieving proper stripping.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the'art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimedis:

1. Apparatus for removing a preselected portion of insulation material from an electrical wire, comprising:

a. a supply of gas,

b. a heater tube including an orifice for directing a stream of c. gas-conducting means coupling the supply of gas with the heater tube,

d. means coupled with said heater tube for controllably heating the gas passing through the tube, and

e. means for passing wire that is insulated with polymer-type material through the stream of heated gas issued from the tube for removing preselected portions of the insulation material by burning.

2. Apparatus for removing preselected portions of insulation material from an electrical wire comprising:

a. a supply of nitrogen gas,

b. gas-conducting means including a gas flow regulator device,

c. gas-heating means coupled with the gas-conducting means and including means for directing a steam of heated gas, and

d. means for passing preselected portions of wire that is insulation coated with polymer-type material through the stream of heated gas for removing the insulation therefrom.

3. Apparatus for removing a preselected portion of insulation material from an electrical wire as defined in claim 2-, further including a continuity testing circuit for determining if the insulation has been effectively removed from the wire.

4. Apparatus for removing a preselected portion of insulation material from an electrical wire, comprising:

a. a supply of nitrogen gas,

b. a gas-filtering means coupled to the gas supply,

c. a gas flow regulator means coupled to the filtering means for regulating the flow of gas,

d. a quartz tube including an orifice for directing a flow of gas and coupled to the gas flow regulator,

e. the quartz tube being equipped with controllable heating means for heating the gas passing therethrough, and

f. means for passing an electrical wire that is insulated with polymer-type, material beneath the orifice in the quartz tube for the purpose of removing preselected portions of the insulation material by burning.

5. Apparatus for removing a preselected portion of insulation material from an electrical wire as defined in claim 4, further including a test circuit for checking the electrical continuity and determining if the insulation has been effectively removed from the preselected portion of the wire.

6. Apparatus for removing a preselected portion of insulation material from an electrical wire as defined in claim 5, further characterized by the including of audible means in the test circuit for indicating the continuity condition as determined by the test circuit.

7. A process for removing the insulation material from a preselected portion of wire, the method comprising the steps:

1. controllably heating a stream of filtered gas, and

2. passing a selected portion of wire that is insulation coated with polymer-type material through the stream of heated gas for removing the insulation material from the wire.

8. The process for removing a preselected portion of insulation material from an electrical wire as defined in claim 7, and further characterized by the step of electrically testing the portion of wire from which the insulation material has been removed for continuity. 

2. Apparatus for removing preselected portions of insulation material from an electrical wire comprising: a. a supply of nitrogen gas, b. gas-conducting means including a gas flow regulator device, c. gas-heating means coupled with the gas-conducting means and including means for directing a steam of heated gas, and d. means for passing preselected portions of wire that is insulation coated with polymer-type material through the stream of heated gas for removing the insulation therefrom.
 2. passing a selected portion of wire that is insulation coated with polymer-type material through the stream of heated gas for removing the insulation material from the wire.
 3. Apparatus for removing a preselected portion of insulation material from an electrical wire as defined in claim 2, further including a continuity testing circuit for determining if the insulation has been effectively removed from the wire.
 4. Apparatus for removing a preselected portion of insulation material from an electrical wire, comprising: a. a supply of nitrogen gas, b. a gas-filtering means coupled to the gas supply, c. a gas flow regulator means coupled to the filtering means for regulating the flow of gas, d. a quartz tube including an orifice for directing a flow of gas and coupled to the gas flow regulator, e. the quartz tube being equipped with controllable heating means for heating the gas passing therethrough, and f. means for passing an electrical wire that is insulated with polymer-type material beneath the orifice in the quartz tube for the purpose of removing preselected portions of the insulation material by burning.
 5. Apparatus for removing a preselected portion of insulation material from an electrical wire as defined in claim 4, further including a test circuit for checking the electrical continuity and determining if the insulation has been effectively removed from the preselected portion of the wire.
 6. Apparatus for removing a preselected portion of insulation material from an electrical wire as defined in claim 5, further characterized by the including of audible means in the test circuit for indicating the continuity condition as determined by the test circuit.
 7. A process for removing the insulation material from a preselected portion Of wire, the method comprising the steps:
 8. The process for removing a preselected portion of insulation material from an electrical wire as defined in claim 7, and further characterized by the step of electrically testing the portion of wire from which the insulation material has been removed for continuity. 